You can buy these using Love Tokens during the Love is in the Air holiday. They create a random candy with one of several phrases. The candies are needed for the achievement Be Mine! which is needed for the holiday's meta, Fool For Love, which is in turn needed for the main holiday meta What a Long, Strange Trip It's Been. Because of the randomness of the candies and the fact you will need eight different ones to complete the achievement, you may need to purchase several bags to get them all.